This is not true. Too many people I know go for experimental treatments overseas including people I know really can't afford it but somehow get the money together and most of those treatments are untried and a waste of money. I have known too many people who, being diagnosed with serious, life threatening cancer, have done this, in actual fact.
So do I think it's unlikely if you have a validated treatment that will likely also be approved here and that doctors at top research institutions recommend here, that people 1) would not hear if it; and 2) that some number would not seek to get that treatment? Is it the masses that everyone would hope for, no. It's off-label. Yes, it's out of pocket and it's not for everyone to do that, or to find the resources to do it. It would be a limited part of that patient population. But not everyone is without resources in the families or more broadly including friends and family.